Plastic and glass containers or bottles are prevalent in a wide variety of shapes and sizes for holding many different types of materials such as detergents, chemicals, motor oil, beverages, etc. These containers are glass or plastic (mono or multi layers) of polyethylene, polypropylene, polyester or vinyl along with other specialty blends for specific barrier and product resistance performance. These containers are typically provided with a label which designates the trade name of the product and may contain other information.
Labels designed to adhere to glass and/or polyethylene terephthalate (PET) are typically applied using a cold or hot glue application processes. During the automated bottle labeling, glue (high viscosity, tacky liquid) is directly applied to the preprinted label and then applied to the bottle. The use of glues, however, requires extensive cleaning as the glue dries and accumulates on the bottling line equipment. In some cases, the glue must be heated prior to application, which requires additional heating equipment and increases energy costs.
In addition to cold- and hot-glue applied labeling methods, preprinted pressure sensitive adhesive (PSA) labels are also used. These labels utilize a release liner to protect the preprinted label face from interacting with the tacky PSA. The use of traditional PSA labels results in several million pounds of liner waste per year in the bottling industry. PSAs also lack removability properties desirable in downstream recycling and bottle reusing facilities.
Attempts to overcome these limitations have been described in the literature. U.S. Pat. Nos. 6,306,242; 6,517,664; and 6,663,746 to Dronzek describe a labeling system for applying labels to plastic and glass bottles. The labeling system includes applying a layer of a hydrophilic solid material to a polymeric label to form a hydrophilic layer on the polymeric label; applying water, water containing a cross-linking agent or a water based adhesive over the hydrophilic layer to form a fastenable polymeric label; fastening the fastenable polymeric label to a glass, plastic or metal container or surface; and curing the polymeric label on the glass, plastic or metal surface or container.
U.S. Pat. No. 7,943,714 to Schneiders describes a labeling system containing a blend of two or more polymers having different hydrophilicities or using a polymer with repeat units having carboxylic, sulfonic or phosphonic acid groups and/or their salts.
Dronzek and Schneiders require the use of non-porous or relatively non-porous face sheets, such as polypropylene, high/low density polyethylene, polyethylene terephthalate, polystyrene, polycarbonate, vinyl and compatibilized blends. Face sheets prepared from these materials typically have a moisture vapor transmission rate of less than about 150 g/m2/24 hr as measured using the TAPPI T448 om-09 standard protocol. In fact, Schneiders discloses that the use of porous face sheets, i.e., those having high moisture vapor transmission rates (MVTR) values, with pressure sensitive adhesives is undesirable because the finished labels exhibit poor wet tack and swimming. Similar disadvantages are described in Dronzek.
There exists a need for a clean, liner-free labeling solution for glass and polyethylene terephthalate (PET) automated bottle labeling applications that provides long term label to bottle adhesion when dry and long term adhesion when exposed to ice water condition for extended time periods, particularly for substrates having high MVTR values.
Therefore, it is an object of the invention to provide improved liner-free labels that provide long-term adhesion to a desired substrate, but can be readily removed when needed, such as in standard recycling or reuse facilities.
It is yet a further object of the invention to provide improved methods for applying a liner-free label to a substrate.
It is a further object of the invention to provide a clean, glue-free, liner-free labeling solution for glass and polyethylene terephthalate (PET) automated bottle labeling applications that provides long term label to bottle adhesion when dry and long term adhesion when exposed to ice water conditions for extended time periods.
It is also an object of the invention to provide a clean, glue-free, liner-free labeling solution for glass and polyethylene terephthalate (PET) automated bottle labeling applications that provides long term label to bottle adhesion when dry and long term adhesion when exposed to ice water conditions for extended time periods wherein the labels can be readily removed when necessary using methods readily available in bottle recycling and reuse facilities.